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Command vs Actual boost ??

Discussion in 'A3/S3 Forum (8L Chassis)' started by Essflee, Feb 20, 2011.

  1. Essflee
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    Essflee Well-Known Member

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    [Feb 20, 2011]
    Good evening...

    Looking for some input, I took my car for a drive the other day and logged my actual vs requested boost,

    Requested was 1350mb and actual was 1540mb possibly higher due to map sensor being exceeded...

    After doing some reading up it looks lightly that I've got a boost pipe come loose or split somewhere possibly going to the N75, I'm going to have a nose about the engine bay tomorrow and see if I can see anything obvious. The car is due for it's 500mile oil service on Friday so I didnt really want to drive back upto Jabba which is over 110 miles from me before I've had that done.

    Question is, is the car alright to drive while I'm seeing such a difference in boost pressure ? I've been keeping off heavy boost for obvious reasons

    Cheers
    #1
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  3. NHN
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    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    [Feb 20, 2011]
    Depends if the logs show a constant difference or split millisecond, as these measurements are in milliseconds huh chap, its not a huge difference either, have you got the original logs so others can peruse over, Badger is a good person to ask for this.
    #2
  4. Essflee
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    Essflee Well-Known Member

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    [Feb 20, 2011]
    To be honest Nigel I only went out in the car to check the boost as I've had it wound back a bit, was only on a liquid gauge also...

    I didn't go crazy with the revs as the engine is still going through the run in period, just took it up to roughly 4k rpm, the actual boost shot to 1540mb under full load and stayed there long enough for me to pull say from 2.5krpm up to 4krpm, Seemed pretty constant, command was the same, only at 1350mb...

    Bit paranoid about the motor at the moment, want to keep this engine a good'un :)
    #3
  5. sportstractor
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    sportstractor Chugger

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    [Feb 20, 2011]
    yeah I would also be looking at the n75 and surrounding pipework if its consistant. And I would have thought it would throw it into limp mode under such conditions? I would also be careful, overboosting is a killer
    #4
  6. NHN
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    NHN Retrofitter - Audi - VW - Skoda - Seat Site Sponsor VCDS Map User

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    [Feb 20, 2011]
    TBH mate then best bet is to get some proper logs to check over a period with vcds, liquid is a good idea, but kind of novelty addition if we're honest, it has its uses dont get me wrong, but in circumstances like these mate, vcds imho is the best system to use, so it can maybe help alleviate your worry or at least help track down issues.
    #5
  7. Welly
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    Welly VX220 SC Driver :)

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    [Feb 20, 2011]
    Lots of this happening at the moment for unknown reasons. Seems strange to have a bunch of the same problems all at the same time?

    Same old same old advice though, too much boost - start with checking N75 pipework.
    #6
  8. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Feb 21, 2011]
    get a real boost gauge.. else you are blind!
    #7
  9. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Feb 21, 2011]
    I think our beloved cars have hit the magic age where the pipe work is perishing. It's like hitting that age where you require a hip replacement :)

    I will be ordering one of these ASAP after my recent issues and now knowing the map sensor is maxed on VCDS.
    #8
  10. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Feb 21, 2011]
    rubber parts and VAG's just dont go..
    VAG seem to have used some of the worst grade rubber for the application of oil fumes, pressure, temperature etc... and now they're old, silly pipes perishing, splitting, etc are contributing to all sorts of running issues.

    Thankfully however, a lot of the vac system is not required for the engines running and can be simplified, so investing some time and £ in replacing the hoses with silicon ones, whilst simplifying the plumbing will make for a more reliable engine.
    #9
  11. Essflee
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    Essflee Well-Known Member

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    [Feb 21, 2011]
    Cheers for the help lads, these vacuum/boost pipes are a proper pain in the arse,

    Should have bought an R32 :)
    #10
  12. Welly
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    Welly VX220 SC Driver :)

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    [Feb 21, 2011]
    :slap:
    #11
  13. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Feb 21, 2011]
    Silicone it up lads! I've just bought £50 worth off "Mr Silicone's" shop on ebay. I'm not going to let rubber ruin my fun!!! erm maybe that saying applies to other things too ;)
    #12
  14. Welly
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    Welly VX220 SC Driver :)

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    [Feb 21, 2011]
    So the new S3 owner's motto isn't 'Strap it up before you slap it up'....
    #13
  15. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Feb 21, 2011]
    Dont be a fool, wrap your tool!
    #14
  16. Piester
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    Piester Member

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    [Feb 22, 2011]
    Westle - what sizes/length silicon did you order? I'm thinking about getting a load and replacing whatever I can see, just don't have much of a clue what quantity and diameters to by.

    I replaced all the PCV pipework with OEM last year, and have the 3" TIP silicone, but everything else is stock and pretty bloody old. Any recommendations?

    Cheers
    #15
  17. Westy
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    Westy Double Dark Side! Diesel & 8P

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  18. Essflee
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    Essflee Well-Known Member

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    [Mar 17, 2011]
    Just been to see a gentlemen who works for Revo as he's close to me to see if he could do some logs for me on vcds regarding my requested vs actual boost...

    On first driving the car he said it feels like a nice map, did his checks and the absolute boost pressures were spot on, so...

    Some advice is with the liquid gauge, take it's readings with a large pinch of salt...
    #17
  19. Welly
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    Welly VX220 SC Driver :)

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    [Mar 17, 2011]
    Why? The data is the exact same data that vag com will be reading....
    #18
  20. Essflee
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    Essflee Well-Known Member

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    [Mar 17, 2011]
    I agree, that's what I said to him but the results told a different story.

    Out curiosity what block do you log vcds, is it 115 ?
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  21. Welly
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    Welly VX220 SC Driver :)

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    [Mar 17, 2011]
    Yep, 115 for requested vs actual.

    My Liquid is always spot on.
    #20
  22. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Mar 17, 2011]
    Yep 115 is boost, actual V requested
    #21
  23. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Mar 17, 2011]
    Snap!
    #22
  24. Essflee
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    Essflee Well-Known Member

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    [Mar 17, 2011]
    Most I saw on vcds was 2400mb actual, requested was around the 2380mb area, when I've used the liquid gauge the actual boost was going in excess of 2540mb... Strange.
    #23
  25. Westy
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    Westy Double Dark Side! Diesel & 8P

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    [Mar 17, 2011]
    The map sensor maxes out at 2400mb so you wont see any more than that. You'll need a proper boost gage to get an accurate boost reading.
    #24
  26. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Mar 17, 2011]
    please explain more..
    liqui talks to ecu and reads the same data as vagcom...
    sensor maximum if hardware on map sensor, so if you, vagcom, or liqui see 2550mb at any point you dont know whether its at 2550mb or above it, as the sensor is at its maximum..

    What was logged and how to confirm it was a "nice map"
    #25
  27. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Mar 17, 2011]
    sample rate used? what gear? etc etc, actual logs?

    same raw data fella
    #26
  28. Essflee
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    Essflee Well-Known Member

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    [Mar 17, 2011]
    The map sensor maxes out at 2540mb
    #27
  29. Essflee
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    Essflee Well-Known Member

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    [Mar 17, 2011]
    Bill, I agree with what your saying regarding both vagcom or liquid reading of map sensor.

    All I'm saying is I explained to this bloke how I was seeing more boost than requested so he hooked up his lap top I read various blocks, not sure exactly which ones but I remember block 115 was fir the absolute pressures.

    The reading from block 115 were spot on and little deviance between requested and actual which made me look probably to this guy that I was worrying about nothing.

    He said it felt like a good map only through driving for a few minutes before doing any logging,

    He has worked for revo for more than 7 years and said my car seemed fine and that charging me for a new map would be silly...

    The runs were done in 3rd and 4th

    As we only saw a maximum of 2400mb of boost through vcds which is well in the limits of the map sensor I went away happy, though as usual coming on this forum has raised doubt for a change...

    I didn't think you could get any more accurate that vcds with in reason, the readings seemed to tie right in with what Jabba had told me,
    #28
  30. [Dave B]
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    [Dave B] Rrrrrrrr-tech

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    [Mar 17, 2011]
    If you're running a jabba map I'd expect to see command boost at higher than 2400mbar at some point, with actual boost trailing behind it until full spool is reached (unless you have a boost leak). Has anyone near you got vagcom that can log it in third gear and give you the data? Posting it up on here will help the helpful chaps on here give advice.

    After working through the issues with my car the command vs actual numbers looked like this:

    [​IMG]
    #29
  31. Essflee
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    Essflee Well-Known Member

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    [Mar 17, 2011]
    Dave, I went back to Jabba a few weeks ago and asked them to drop the boost a little so there wasn't so much torque which they did so it was originally higher. I asked him to set the boost to about 2350mb so it was still quick but not maxed out which he did...

    When I got home I tried the liquid gauge and it was saying that actual was higher than requested, when I spoke to kev at Jabba he said that when he took it out he wasn't seeing anymore than 2400mb but I was welcome to take it back if I wasn't happy.

    However I found a guy locally who does revo and he plugged his laptop in to see what was going on and gave me pretty much the same answer than kev at Jabba had already given me..
    #30
  32. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Mar 17, 2011]
    If I recall it was you who said YOU had higher readings than 2400mb before did you not?
    if its doign as you say all fine and dandy, it was your previous >2550mb readings and issues which prompted this discussion at all
    #31
  33. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Mar 17, 2011]
    stick it in 6th, from 2krpm and floor it..
    bet you see >2400mb
    (normal high load response from the ecu btw)
    #32
  34. Essflee
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    Essflee Well-Known Member

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    [Mar 17, 2011]
    Exactly.

    I've been told from 2 different reputable tuners that my car is running fine, ie actual vs requested,

    However when looking myself with the liquid gauge the actual gies off the map sensor leading me to believe the liquid gauge is *****, but then I'm told that it uses the same information that vcds does, hence it's a bit confusing, but hey ho, don't want to develop this into a yarn... :)
    #33
  35. Essflee
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    Essflee Well-Known Member

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    [Mar 17, 2011]
    Didn't realize this either, cheers !
    #34
  36. gez
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    gez S3 hunter

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    [Mar 17, 2011]
    I dont know why the n75 gets its boost pressure from the charge pipe and not the inlet manifold. Ive changed mine round so the n75 gets 22psi from the engine which is more accurate. Try doing that and see if it makes a difference. That to me is making sure requested boost is actuall boost. Make sense??
    #35
  37. s3dave
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    s3dave TFSI Hybrid

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    [Mar 17, 2011]
    Yes but if there is a difference there is a problem, so you maybe masking boost leaks doing that...
    #36
  38. gez
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    gez S3 hunter

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    [Mar 17, 2011]
    No, there will be a massive pressure drop from the charge pipe to the manifold. When the chargepipe sends 22psi to the n75 it would be 18or so at the inlet manifold.
    Your not masking any boost leaks. Your giving n75 actuall boost pressure when entering the engine.
    #37
  39. Sandip
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    Sandip Well-Known Member

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    [Mar 17, 2011]
    Gez is this how it would be done?

    Bung up the chargepipe and run a vac line to the inlet instead
    [​IMG]
    #38
  40. s3dave
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    s3dave TFSI Hybrid

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    [Mar 17, 2011]
    So does the ecu compensate for this? as my actual v requested is spot on, all im saying if your having problems, and your moving pipe work about your masking something that is or was run as intended but was not working correctly, if you know what i mean
    #39
  41. gez
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    gez S3 hunter

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    [Mar 17, 2011]
    Yes sandip
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